High-efficiency electrocatalytic hydrogen evolution in NiCo-Mo₂C tandem nanoreactors with bimetallic modulation and crystal plane synergy

Mo₂C, with an electronic structure closely resembling that of Pt, holds significant promise as a catalyst for nonprecious metal-based electrocatalytic hydrogen evolution reactions (HER). This study presents the design and synthesis of Ni and Co bimetallic-doped Mo₂C (NiCo-Mo₂C) tandem nanoreactors, engineered by leveraging the concept of a high-gain transistor cascade amplifier. In NiCo-Mo₂C material, each monomer layer on Mo₂C rod functions as an individual electrocatalytic nanoreactor, with the rod supporting a tandem configuration of these units. The combined modulation of Ni and Co at NiCo-Mo₂C interface increases the electron cloud density around Mo and shifts the d-band center negatively, effectively reducing Mo-H* binding energy. The synergy between NiCo-Mo₂C (101) and (002) crystal planes facilitates both water dissociation and H* desorption from Mo sites. This tandem configuration of multicatalytic units achieves enhanced hydrogen evolution, demonstrated by the low overpotential at 10 mA·cm^-2 (η₁₀) values of 129 mV and 180 mV and Tafel slopes of 84 mV·dec^-1 and 85 mV·dec^-1 in 1 M KOH and 0.5 M H₂SO₄, respectively. Through bimetallic modulation, crystal plane synergy, and tandem structuring, this work advances a novel approach to optimizing HER kinetics, presenting a valuable strategy for developing highly efficient, nonprecious metal-based electrocatalysts.